Suspension strut for a vehicle

ABSTRACT

A hydraulic strut system that damps vehicle vibration and includes a compressible fluid, a strut, and a valve plate. The strut includes three concentric tubes defining an inner cavity, an intermediary cavity, and an outer reservoir cavity, the inner cavity and intermediary cavity being fluidly coupled, wherein the inner cavity receives a piston that divides the inner cavity into a first volume and a second volume, the piston having an aperture that allows one way flow from the first volume to the second volume. The valve plate is removably coupled to the strut, and includes a first fluid path that allows one-way fluid flow from the intermediary cavity to the reservoir cavity, the first fluid path including a damping valve that damps fluid flowing therethrough; and a second fluid path that allows one-way fluid flow from the reservoir cavity to the inner cavity, the second fluid path further including a replenishment valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 14/029,139, filed 17 Sep. 2013, which is a continuation of U.S.patent application Ser. No. 13/176,720, filed 5 Jul. 2011, which claimsthe benefit of U.S. Provisional Application Nos. 61/361,493 filed 5 Jul.2010 and 61/423,573 filed 15 Dec. 2010, all of which are bothincorporated in their entirety by this reference.

This application is related to U.S. Pat. Nos. 6,811,167 and 6,988,599,which are both incorporated in their entirety by this reference.

TECHNICAL FIELD

This invention relates generally to the damper field, and morespecifically to an improved suspension strut in the vehicle suspensionfield.

BACKGROUND

There are a variety of dampers in automotive suspensions, including amono-tube type strut, a twin-tube type strut, and a triple-tube typestrut. Within each variation, there are variations with valvearrangement and fluid management. The triple-tube type strutconstruction includes tube and valve arrangement that allows for fluidflow within the strut that is generally in a single direction for boththe compression and rebound direction of the suspension strut, whereasboth mono-tube and twin-tube type struts require fluid to flow indifferent directions for the compression and rebound directions. Thissingle-direction property of the triple-tube type strut allows fordamping control of the fluid flow within the triple-tube type strut tobe localized to one general area within the strut for both compressionand rebound directions. As a result, conventional semi-active orcontinuously variable damping control systems typically utilize thetriple-tube type strut and a single active solenoid valve to controldamping force for both the compression and rebound directions of thestrut.

Conventional triple-tube type strut dampers include many internal partsthat function to tune the dampening properties of the strut and are, forthis reason, quite complex. Additionally, the damping mechanisms thatare utilized in such triple-tube type struts may leak, decreasing theefficiency of the damper, or may be relatively expensive. As shown inFIG. 1 (prior art), the active valve 10 in typical triple-tube typestrut dampers is often mounted perpendicular to the long axis of thedamper tube 12 and substantially adjacent to the base valve 14 thatallows replenishment flow to the inner cavity 16 during the reboundstroke of the strut. This may allow such triple-tube type strut dampersto increase the range of travel of the suspension strut given a totalstrut height. However, this arrangement requires a fastening mechanismthat does not benefit from the compressive forces from tube assemblyand/or the vehicle. In semi-active or continuously variable dampingcontrol systems that utilize compressible fluids where the pressurewithin the suspension strut may increase to substantially high levels,the fastening mechanism used to mount the active valve perpendicularlyto the axis of the damper tube may become substantially costly towithstand such high pressures. Because of complexity of typicaltriple-tube type strut dampers, cost is relatively high and adoption ofsuch semi-active or continuously variable damping control systems in thefield is substantially impaired.

Thus, there is a need in the vehicle suspension field to create animproved suspension strut. This invention provides such strut.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of a semi-active suspension strutof the prior art.

FIGS. 2A and 2B are schematic representations of the suspension strut ofthe preferred embodiments with the displacement rod and cavity pistondisplaced away from the valve plate and with the displacement rod andcavity piston displaced toward the valve plate, respectively.

FIGS. 3A, 3B, and 3C are schematic representations of the valve platewith a passive damper valve in an orthogonal view, taken along Line A-Ain FIG. 3A with the damping flow path, and taken along Line B-B in FIG.3A with the replenishment flow path, respectively.

FIG. 4 is a schematic representation of flow during the compressionstroke.

FIGS. 5A and 5B are schematic representations of flow during the reboundstroke of the outflow from the pressure chamber and the rebound flowinto the interior cavity, respectively.

FIGS. 6A and 6B are schematic representations of the valve plate with avariation of an actuatable damper valve with decreased damping force andincreased damping force, respectively.

FIGS. 7A, 7B, and 7C are a schematic representation of the valve platewith a first, second, and third variation of a regenerative dampervalve, respectively.

FIG. 8 is a schematic representation of the regenerative suspensionstrut system embodiment.

FIGS. 9A and 9B are schematic representations of flow during thecompression stroke for a first and a second embodiment of theregenerative suspension strut system embodiment, respectively.

FIGS. 10A and 10B are schematic representations of flow during therebound stroke of the outflow from the pressure chamber and the reboundflow into the interior cavity, respectively, for the regenerativesuspension strut system embodiment.

FIGS. 11A and 11B are schematic representations of the valve plate witha passive damper valve in an orthogonal view, taken along Line A-A inFIG. 3A with the damping flow path, and taken along Line B-B in FIG. 3Awith the replenishment flow path, respectively.

FIGS. 12 and 13 are schematic representations of alternative flow pathsof the regenerative suspension strut system of the preferredembodiments.

FIG. 14 is a graphical representation of the operating regions of thesuspension strut and the energy that may be recovered using theregenerative suspension strut system of the preferred embodiments.

FIGS. 15 and 16 are schematic representations of variations of theregenerative suspension system strut with a second compliant volume anda reservoir, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the inventionis not intended to limit the invention to these preferred embodiments,but rather to enable any person skilled in the art to make and use thisinvention.

As shown in FIGS. 2 and 3, the suspension strut 100 of the preferredembodiments is preferably used with a vehicle having a wheel contactinga surface under the vehicle, such as the road, and preferably functionsto suspend the wheel from the vehicle while allowing compressionmovement of the wheel toward the vehicle and rebound movement of thewheel toward the surface. The suspension strut 100 preferably includes acompressible fluid 102; a hydraulic tube 110 including an inner tube 130that defines an inner cavity 132 that contains a portion of thecompressible fluid 102, a secondary tube 140 that substantiallyenvelopes the inner tube 130 and cooperates with the inner tube 130 todefine an intermediary cavity 142 that contains another portion of thecompressible fluid 102 and that accepts fluid flow from the inner cavity132 through an inner flow path, and a housing tube 150 thatsubstantially envelops the secondary tube 140 and cooperates with thesecondary tube 140 to define a reservoir cavity 152 that containsanother portion of the compressible fluid 102; a displacement rod 120; acavity piston 122 coupled to the displacement rod 120 and extending intothe hydraulic tube, thereby separating the inner cavity into a firstvolume 134 and a second volume 136, and that includes an aperture 124that allows flow of fluid from the first volume 134 to the second volume136 during the compression movement of the wheel; and a valve plate 160coupled to the end of the hydraulic tube 110 opposite the displacementrod no that defines a first fluid path 162 from the intermediary cavity142 to the reservoir cavity 152 (also referred to as “damping flow”path) and a second fluid path from the reservoir cavity 152 to the firstvolume 134 (also referred to as “replenishment flow” path), and includesa damper valve 166 that substantially affects the flow of fluid throughthe first fluid path 162. The valve plate 160 may also include aninlet/outlet valve 172 or a regeneration valve 170 that allows foradditional fluid to enter the hydraulic strut 110 and/or extraneousfluid to exit the hydraulic strut 110 (for example, to increase ordecrease, respectively, the suspending force provided by the suspensionstrut 100). The flow of fluid into and/or out of the hydraulic strutthrough the regeneration valve 170 and/or inlet/outlet valve 172 may beactively driven by one or more pumps, such as the digital displacementpump or motor as described in U.S. Pat. No. 5,259,738 entitled “FluidWorking Machine” and issued on 9 Nov. 1993, which is incorporated in itsentirety by this reference, but may alternatively be any other suitabletype of hydraulic pump.

In the preferred embodiments, the hydraulic tube 110 is coupled to thebody of the vehicle and the displacement rod 120 is coupled to the wheelof the vehicle, which decreases the unsprung weight of the vehicle andmay be beneficial in the dynamics of the vehicle. The hydraulic tube 110and the displacement rod 120 preferably cooperate to translate forcesfelt by the wheel into a force substantially along the long axis of thesuspension strut no. The hydraulic tube no preferably includes a vehicleinterface 114 (shown in FIG. 2). Similarly, the displacement rodpreferably includes a wheel interface 126. The vehicle interface 114 andthe wheel interface 126 are preferably non-permanent attachmentinterfaces, for example, an eye that allows for a bolt to couple to thebody of the vehicle or the wheel, screw holes to receive couplingscrews, clips, Velcro, or any other suitable removable attachmentmechanism. However the vehicle 114 and wheel interface 126 mayalternatively be a substantially permanent attachment interface, forexample, a welding joint. However, any other suitable interface type andarrangement of the suspension strut 100 relative to the vehicle may beused.

The suspension strut 100 of the preferred embodiments allows the basevalve as seen in typical struts to also function to dampen the fluidflow within the strut, and functions to combine the dampening mechanism(the damper valve 166) and the base valve into the valve plate 160. Thisprovides a substantially more compact and relatively simple constructionas compared to the prior art (shown in FIG. 1). When desired, a valveplate 160 of any particular valve plate is preferably replaceable withanother valve plate 160. For example, if a first valve plate 160malfunctions, a second valve plate 160 may be swapped in to replace thefirst valve plate 160 to restore function of the suspension strut 100.Similarly, because most of the fluid control is contained within thevalve plate 160, the fluid flow within the strut may be adjusted byusing different types of valve plates 160 without any substantial changeto other components of the suspension strut 100. For example, a firstvalve plate 160 with a first set of fluid flow control andcharacteristics may be replaced with a second valve plate 160 with asecond set of fluid flow control and characteristics relatively easily.Additionally, by placing most of the fluid control within a removablevalve plate 160, the suspension strut 100 may be easily updated withalternative valve plates 160 that provide additional and/or otherfunctions as the application of the strut 100 changes and/or as valveplate 160 designs change. For example, a first valve plate 160 with apassively actuated damper valve 166 may be swapped with a second valveplate 160 with an active damper valve 166, changing the strut 100 from apassive suspension strut to a semi-active suspension strut. This featuremay substantially increase the versatility and adaptability of thesuspension strut 100 by allowing the same suspension strut 100 to berepeatedly used even as applications (or even conditions) may change.

The compressible fluid 102 the preferred embodiments functions to supplythe suspending spring force hydraulic suspension strut. The compressiblefluid 102 is preferably a silicone fluid that compresses about 1.5%volume at 2,000 psi, about 3% volume at 5,000 psi, and about 6% volumeat 10,000 psi. Above 2,000 psi, the compressible fluid has a largercompressibility than conventional hydraulic oil. The compressible fluid,however, may alternatively be any suitable fluid, with or without asilicon component that provides a larger compressibility above 2,000 psithan conventional hydraulic oil.

The hydraulic tube 110 the preferred embodiments functions to containcompressible fluid 102 to provide damping force as the displacement rod120 and the cavity piston 122 is displaced towards (compression stroke)and away from (rebound stroke) the valve plate 160 as the wheel of thevehicle experiences irregularities in the road, for example, as thevehicle turns or encounters bumps. The hydraulic tube 110 is preferablyof a triple-tube construction that allows for substantiallysingle-directional flow within the hydraulic tube 110 during bothcompression and rebound strokes, as shown in FIG. 4 and FIG. 5,respectively. As shown in FIG. 4, during the compression stroke, thedisplacement rod 120 and cavity piston 122 are displaced toward thevalve plate 160. Thus, fluid 102 flows from the first volume 134 of theinternal cavity to the second volume 136 through the aperture 124 of thecavity piston 122. Because of the displacement rod 120 that is coupledto the cavity piston 122 and occupies a portion of the volume of thesecond volume 136, a portion of the fluid 102 is displaced into theintermediary cavity 142 from the internal cavity 132 through an innerflow path. The inner flow path fluidly couples the intermediary cavity142 to the internal cavity 132 near or below the lowest stroke point ofthe cavity piston 122, and is preferably a valve in a second valveplate, but may alternately be an aperture through the inner tube wall,connection tubing or any other fluid connection. From the intermediarycavity 142, the fluid flows through the first fluid path 162 of thevalve plate 160 to the reservoir cavity 152. As the fluid 102 flowsthrough the first fluid path 162, the fluid 102 flows through dampervalve 166, which provides a damping force to the fluid 102 and,subsequently, to the suspension strut 100. As shown in FIG. 5A, duringthe rebound stroke, the displacement rod 120 and cavity piston 122 aredisplaced away from the valve plate 160. The aperture 124 preferablyincludes an aperture valve that is preferably a one-direction valve,fluid flow from the first volume 134 into the second volume 136 ispermitted and flow from the second volume 136 into the first volume 134is prevented. Thus, as the second volume 136 is decreased during therebound stroke, fluid 102 is displaced from the second volume 136 intothe intermediary cavity 142 (as fluid flow into the first volume 134 isprevented by the aperture valve), and follows a path substantiallyidentical to the one described above for the compression stroke.Concurrently, the volume of the first volume 134 increases as thedisplacement rod 120 and cavity piston 122 are displaced away from thevalve plate 160. To prevent aeration, fluid 102 is directed into thefirst volume 134 to replenish the fluid contained in the internal cavity132, as shown in FIG. 5B, and fluid 102 from the reservoir cavity 152 isdirected through the second fluid path 164 of the valve plate 160 intothe internal cavity 132. The valve plate 160 preferably includes areplenishment valve coupled to the second fluid path 164 that ispreferably a one directional valve that opens when the pressure in thefirst volume is decreased as a result of the rebound stroke. Both theaperture valve and the replenishment valve preferably do not increasethe pressure of the fluid flowing through, and preferably allow bothsides of the valve to become substantially equal pressure when the valveis opened. For example, the aperture valve and the replenishment valvemay each be a check valve that allows substantially unhindered flow inone direction and prevents flow in an opposite direction. The aperturevalve and the replenishment valve may alternatively be a butterflyvalve, a ball valve, a diaphragm valve, a needle valve, or any othervalve, and may be either passive or active. However, the aperture valveand replenishment valve may be of any other suitable type andarrangement.

The housing tube 150, secondary tube 140, and internal tube 130 arepreferably steel tubes that withstand the pressure provided by thecompressible fluid during either a compression or rebound stroke. In thesuspension strut 100 of the preferred embodiments, the fluid control ismostly contained within the valve plate 160. This substantiallydecouples fluid control from the housing, secondary, and internal tubesand allows for the housing, secondary, and internal tubes to beoptimized as pressure vessels that better withstand the pressures thatmay be present in a compressible fluid strut system. Because eachvehicle (or “application”) may require different characteristics fromthe suspension strut 100, the geometry of each of the housing,secondary, and internal tubes, may be tailored to each application. Thehousing, secondary, and internal tubes of any suitable geometrypreferably include a valve plate interface that interfaces with thevalve plate 160. The valve plate interface preferably allows for thevalve plate 160 to couple to any suitable geometry of the housing,secondary, and internal tubes. The valve plate interface may include afirst end that is customized for a specific geometry of housing,secondary, and internal tubes and a second end that is adapted to thegeometry of the valve plate 160. Alternatively, the valve plateinterface may be formed into the housing, secondary, and internal tubes.For example, the housing, secondary, and internal tubes may each be adesired geometry for a substantial portion of the hydraulic tube no andtaper into diameters that accommodate for a valve plate 160. However,the valve plate interface may be any other suitable arrangement.

As described above, the valve plate 160 functions to provide most of thefluid control within the suspension strut 100. The valve plate 160preferably defines a first fluid path 162 from the intermediary cavity142 to the reservoir cavity 152 (also referred to as “damping flow”path) and a second fluid path from the reservoir cavity 152 to the firstportion of the inner cavity 132 (also referred to as “replenishmentflow” path), and includes a damper valve 166 that substantially affectsthe flow of fluid through the first fluid path 162. The valve plate 160is preferably mounted to the end of the hydraulic tube 110 opposite ofthe displacement rod, as shown in FIGS. 2 and 3, but may alternativelybe arranged in any other suitable location. As shown in FIGS. 2A, 2B,and 3A, the valve plate 160 is preferably clamped onto the housing,secondary, and inner tubes using a cap 180. The cap 180 may include aplurality of holes that receive bolts that function to apply pressureonto the cap 180 to clamp the valve plate 160 onto the tubes 150, 140,and 130. However, the valve plate 160 may be assembled to the hydraulictube no using any other suitable mechanism or arrangement. The valveplate 160 may also include a sealant, such as o-rings, thatsubstantially seal the interface between the valve plate 160 and thehousing, secondary, and inner tubes to substantially prevent fluidleakage.

As shown in FIG. 3B, the valve plate 160 defines a first fluid path 162between the intermediary cavity 142 and the reservoir cavity 152. Adamper valve 166 is coupled to the first fluid path 162 to substantiallyaffect the flow of fluid 102 through the first fluid path 162, providingthe damping force on the fluid 102 and, subsequently, the suspensionstrut 100. The damper valve 166 is preferably a passive valve in a firstvariation, a manually actuated valve in a second variation, an activevalve in a third variation, or a regenerative valve in a fourthvariation.

In the first variation, the damper valve 166 is a passive valve. Thepassive damper valve 166 is preferably a one directional valve thatallows fluid flow when the pressure difference between a first side(side closest to the intermediary cavity 142) and the second side (sidecloset to the reservoir cavity 152) is at a certain level. The dampervalve 166 of the preferred embodiments is preferably a disc valve (orshim stack) where fluid deflects the disc valve in one direction when acertain pressure differential is reached between either side of the discvalve, opening the valve for fluid flow, and where the disc valveprevents fluid flow in the opposite direction. Disc valves, which aregenerally robust, reliable, and consistent, are often used in a dampervalve. Because typical semi-active or continuously variable dampingcontrol systems require active damper valves, however, disc valves(which are generally passive damper valves) are typically not used intriple-tube type strut architectures. Further, because of the fluid flowpaths in such systems, it is difficult-to-impossible to apply a discvalve within a conventional semi-active or continuously variable dampingcontrol systems that utilize the triple-tube type strut. The valve plate160 of the preferred embodiments, however, allows for a disc valve to beused in a triple-tube type strut architecture by, as shown in FIG. 3B,defining a first fluid path 162 that directs fluid flow in a flowdirection suitable for a disc valve from the intermediary cavity 142 anddirects flow from the disc valve to the reservoir cavity 152.Additionally, as will be described later, the same disc valve may beconverted into a manually actuated or active arrangement. However, thedamper valve 166 of the first variation may be any other suitable typeof passive damper valve, such as a check valve, a ball valve, checkvalve, or needle valve.

In the second variation, the damper valve 166 is a manually actuatedvalve. As an example, a technician may use the manually actuated valvedamper valve 166 to adjust the damping characteristics of the suspensionstrut 100. The manually actuated damper valve 166 may be a bi-statevalve that allows for a high damping force state and a low damping forcestate, but may alternatively be variable with a plurality of degrees ofdamping forces. As mentioned above, the disc valve exhibits dampingproperties that are desirable in a damper valve. Thus, the damper valve166 of the second variation preferably includes a disc valve and anactuator 167, as shown in FIGS. 6A and 6B. The actuator 167 of thesecond variation of the damper valve 166 is preferably a manualactuator. The actuator 167 preferably includes a piston 169 that isarranged over the disc valve that functions to provide an adjustablepressure onto the disc valve to adjust the damping force provided by thedisc valve. More specifically, because fluid flow must deflect the discvalve in order to flow through the valve, by applying a pressure ontothe disc valve through the piston 169, the force necessary to deflectthe disc valve increases, increasing the damping force on the fluid 102flowing through the disc valve. In a first version of the actuator 167of the manually actuated damper valve 166, the actuator 167 may includea screw coupled to the piston 169 that is accessible by a user. Toadjust the damping force provided by the disc valve, a user may tightenthe screw to push the piston 169 towards disc valve. In a second versionof the manually actuated damper valve 166, the valve plate 160 mayfunction to define a third fluid path 165 that directs fluid 102 fromthe intermediary cavity 142 to the reservoir cavity 152, as shown inFIGS. 6A and 6B. The third fluid path 165 preferably passes over the topof the piston 169, applying a fluid pressure across the top of thepiston 169. Because damping force is preferably applied to the fluid 102that flows from the intermediary cavity 142 to the reservoir cavity 152,a portion of the already existing flow between the intermediary cavity142 and the reservoir cavity 152 may be relatively easily directedacross the piston 169 when a damping force is desired. The actuator 167of this variation preferably includes a fluid flow valve 163 that ismanually actuated, for example, a needle valve, which is coupled to thethird fluid path 165 downstream of the piston 169. By adjusting the rateof fluid flow through the third fluid path 165, the pressure provided bythe fluid 102 onto the piston 169 may be adjusted. As shown in FIG. 6B,when the fluid valve 163 is closed, fluid flows into the third fluidpath 165, but cannot flow into the reservoir cavity 152, resulting inincreased fluid 102 pressure onto the piston 169, and subsequently,increased damping force provided by the damper valve 166. As shown inFIG. 6A, when the fluid valve 163 is open and fluid flows through thethird fluid path 165 into the reservoir cavity 152, the pressure appliedby the piston 169 is low, as the pressures in the first 134 and third165 flow paths are substantially equivalent. However, the manuallyactuated damper valve 166 may be of any other suitable arrangement.

In the third variation, the damper valve 166 is an active valve,allowing the suspension strut 100 to function as a semi-activesuspension strut. The active damper valve 166 may be a bi-state valvethat allows for a high damping force state and a low damping forcestate, but may alternatively be variable with a plurality of degrees ofdamping forces. The active valve variation of the damper valve 166 ispreferably used to provide substantially instantaneous adjustments ofthe damping force provided by the suspension strut 100, preferablyduring use in a vehicle while the vehicle is in motion, for an example,if a bump in the road is detected or if the vehicle makes a sudden turn.As mentioned above, the suspension strut 100 may also be used with anactive control suspension system, which may function to actively changethe suspending force provided by the suspension strut 100 by increasingor decreasing the amount of fluid 102 contained within the suspensionstrut 100. Vehicle dynamics may be controlled on more than one level bycombining a semi-active suspension strut 100 with an active controlsuspension system, providing a vehicle that can substantially quicklyadapt to a vast variety of driving conditions. The active damper valve166 is substantially similar to the manual damper valve 166 as describedabove. The active damper valve 166 preferably also includes a disc valveand an actuator 167, as shown in FIGS. 6A and 6B. The actuator 167 ofthe third variation of the damper valve 166 is preferably an activeactuator that may be electronically actuated, for example, by aprocessor or remotely by a user. The active actuator 167 preferably alsoincludes a piston 169 that is arranged over the disc valve thatfunctions to provide an adjustable pressure onto the disc valve toadjust the damping force provided by the disc valve. A first variationof the actuator 167 of the active damper valve 166 is substantiallysimilar to the first variation of the actuator 167 of the manuallyactuated damper valve 166. The actuator 167 of the active damper valve166 of the first variation includes a motor that is coupled to a screwthat functions to raise or lower the piston 169 away from or towards thedisc valve, adjusting the damping force provided by the disc valve. Asecond variation of the actuator 167 of the active damper valve 166 issubstantially similar to the second variation of the actuator 167 of themanually actuated damper valve 166. The valve plate 160 functions todefine a third fluid path 165 that directs fluid 102 from theintermediary cavity 142 to the reservoir cavity 152 to provide pressureacross the top of the piston 169, thus adjusting the pressure providedby the piston onto the disc valve and adjusting the damping forceprovided by the disc valve. The actuator 167 of the active damper valve166 of the second variation includes a fluid flow valve 163 that isactive, for example, a pilot valve that is actuated by a solenoid or anyother suitable type of actuated fluid valve, coupled to the third fluidflow path 165 downstream of the piston 169. The fluid flow valve 163functions provide control of the fluid flow through the third fluid path165 substantially identical to the manual fluid flow valve 163. In athird variation, the stiffness of the damper valve may be electronicallycontrolled by using materials that exhibit different strain propertieswith the application of heat or electricity, or by using electromagnets.However, the active damper valve 166 may be of any other suitablearrangement.

In the fourth variation, the damper valve 166 is a regenerative valve,as shown in FIG. 7. In this variation, the damper valve 166 may beeither passive or active. As fluid flow is damped, a significant amountof energy is dissipated. In conventional dampers, the energy isdissipated as heat and substantially wasted. The damper valve 166 of thefourth variation, however, provides a method and means to harness theenergy, in particular, to convert the energy into electrical energy. Ina first example, shown in FIG. 7A, the damper valve 166 may include animpeller that is coupled to a motor. As fluid flows past the impeller,the impeller is caused to spin, and the energy used to spin the impelleris used to generate electricity in the generator. The fluid 102 isdamped as a result because of the work used to spin the impeller. In thepassive version of the damper valve 166 of the fourth variation, thework required to spin the impeller is substantially constant at alltimes. In the active version of the damper 166 of the fourth variation,increasing the electrical generation required from the generator mayincrease the work required to spin the impeller, increasing the dampingof the fluid 102 (examples shown in FIGS. 7B and 7C). However, any othervariation of a damper valve 166 that is regenerative may be used.

As described above, the first, second, and third variations (andpotentially the fourth variation) all preferably utilize a similarconstruction that includes a disc valve. Because of this feature, it isconceivable that the same housing for the valve plate 160 may be usedwith different variations of the damper valve 166, allowing a valveplate 160 that was outfitted with a passive damper valve 166 to beupgraded to an active damper valve 166 with the same housing for thevalve plate 160.

The valve plate 160 preferably includes one of the above variations ofdamper valve 166, but may alternatively include any number or suitablecombinations of the above variations. For example, the regenerativedamper valve 166 of the fourth variation may be combined with thepassive damper valve 166 of the first variation. More specifically, thevalve plate 160 of this variation may also include both animpeller/generator assembly and a disc valve that cooperate to providetwo fluid flow paths in situations with substantially high volume offluid flow that a regenerative valve alone may not be able toaccommodate. Additionally, because the regenerative valve includes asubstantial number of moving parts, the regenerative valve may fail andprevent fluid from flowing through. By allowing a second path for fluidflow, the suspension strut 100 may continue to function. However, thevalve plate 160 may be any other suitable variation. As mentioned above,the suspension strut 100 of the preferred embodiments preferably allowsfor different valve plates 160 to be used with the same hydraulic tubebody, meaning a suspension strut 100 that originally used a valve plate160 with a damper valve 166 of the first variation may be exchanged witha valve plate 160 with a damper valve 166 of the second, third, orfourth variation, allowing the suspension strut 100 to functiondifferently without substantial changes to any other component of thesuspension strut 100.

As shown in FIG. 8, the suspension strut system 100 may additionallyinclude a regenerative valve and a pump, fluidly coupled to the firstfluid path 134, to form a regenerative suspension strut 101. Much likethe fourth variation of the damper valve, the regenerative suspensionstrut 101 functions to regenerate energy from fluid flow within thestrut, and is preferably also operable in non-regenerative modes. Theregenerative suspension system 101 may additionally include a third flowpath 165 (“regenerative fluid path” or “pump path”), to which theregenerative valve and pump are coupled, wherein the third flow pathfluidly couples the intermediary cavity to the reservoir cavity throughthe valve plate, preferably in parallel with the first flow path 134,more preferably sharing an inlet and an outlet with the first flow path134. The regenerative suspension strut system 101 preferably operates ina first mode that provides a damping force substantially internallywithin the suspension strut 100 by directing the displaced compressiblefluid 102 to a damper valve 166 and a second mode that provides adamping force substantially external to the suspension strut 100 bydirecting the flow of compressible fluid 102 into the pump 190 to drivethe pump 190 and recover energy. In the second mode, the force requiredto drive the pump 190 provides the damping force. The regenerativesuspension strut system 101 may include a third mode where the dampingforce is provided both through the damper valve 166 and by directingflow of compressible fluid into the pump 190 and/or a fourth mode wherethe pump 190 pumps fluid 102 back into the suspension strut 100. Thedamper valve 166 and the regeneration valve 170 may be thought of asoperating in parallel such that fluid flow from the strut 100 may flowto either valve depending on the state of the valve. Alternatively, thedamper valve 166 and the regeneration valve 170 may be the same physicalvalve with multiple modes to function to direct fluid into the pump 190,to dampen fluid 102, and/or to both direct fluid into the pump 170 andto dampen the fluid 102. Similarly, to maintain operation of suspensionstrut 100 when the processor and/or the electronics of the damper valve166 and/or the regeneration valve 170 fail, the damper valve 166 ispreferably of the type of valve where the failure mode still providessubstantial damping force (for example, for a damper valve 166 that is ashim stack valve that increases damping force with increasing stiffness,the shim stack preferably fails in a semi-stiff orientation) to thesuspension strut 100. However, any other suitable arrangement of thedamper valve 166 and the regeneration valve 170 may be used.

The flow pattern of the regenerative suspension strut 101 during thecompression stroke is preferably substantially similar to that describedabove. As shown in FIG. 9, during the compression stroke, thedisplacement rod 120 and cavity piston 122 are displaced toward thevalve plate 160. Thus, fluid 102 flows from the first volume 134 of theinternal cavity to the second volume 136 through the aperture 124 of thecavity piston 122. Because of the displacement rod 120 that occupies aportion of the volume of the second volume 136 and is coupled to thecavity piston 122, the volume available for the displaced compressiblefluid 102 to occupy is less in the second volume 136 than in the firstvolume 134, and the pressure of the fluid within the second volume 136increases. A portion of the fluid 102 may be displaced into theintermediary cavity 142 from the internal cavity 132 and, from theintermediary cavity 142, the fluid flows through the first and/or thirdfluid path 162 of the valve plate 160. In the first mode, thecompressible fluid 102 is then directed to the damper valve 166 to applya damping force on the compressible fluid 102 (shown in FIG. 8). In thesecond mode, the fluid 102 is directed through the regeneration valve170 to the pump 190 to drive the pump 190 and to recover energy.Alternately and/or additionally, in the third mode, the fluid 102 isdirected to both the damper valve 166 and the regeneration valve 170(shown in FIGS. 9 and 11A). However, any other suitable arrangement ofthe flow during the compression stroke may be used.

Likewise, the flow pattern of the rebound stroke is substantiallysimilar to that described above. As shown in FIG. 10A, during therebound stroke, the displacement rod 120 and cavity piston 122 aredisplaced away from the valve plate 160. The aperture 124 preferablyincludes an aperture valve that is preferably a one-direction valve thatonly allows fluid flow from the first volume 134 into the second volume136 and not from the second volume 136 to the first volume 134. Thus,the fluid pressure within the second volume 136 is again increased andfollows a path substantially identical to the one described above forthe compression stroke, potentially further driving the pump 190 torecover energy during the rebound stroke. Fluid 102 is directed into thefirst volume 134 from a compliant volume 191 (as shown in FIG. 8) toprevent aeration within the first volume 134 as the suspension strut 100extends, as shown in FIG. 10B. This compliant volume 191 may be thereservoir cavity 152, such that fluid 102 from the reservoir cavity 152is directed through the second fluid path 164 of the valve plate 160into the internal cavity 132, as shown in FIG. 10. The valve plate 160preferably includes a replenishment valve coupled to the second fluidpath 164 that is preferably a one-directional valve that opens when thepressure in the first volume is decreased as a result of the reboundstroke.

As shown in FIGS. 8, 12 and 13, the regenerative suspension strut system101 may function to direct the compressible fluid 102 to only the dampervalve 166 (the first mode), only the regeneration valve 170 (the secondmode), or to both the damper valve 166 and the regeneration valve 170(the third mode). The regenerative suspension strut system 101 mayinclude a processor that determines the mode depending on the usescenario, the user preferences, and/or any other suitable factor. In afirst example, directing fluid through the regeneration valve 170 andinto the pump 160 to drive the pump may provide a substantially slowerdamping response than directing fluid into the damper valve 166. In thisfirst example, when the processor detects a maneuver of the vehicle thatrequires a faster suspension response, for example, during a fast turnor a substantial bump in the road, the processor may select to operatein the first mode. In a second example, a user may select to operate inthe first mode because of the increased responsiveness of the suspensionsystem. For example, the user may plan on driving quickly on mountainroads that include a substantial number of turns. In a third example,the user may know that the road ahead contains a substantial amount ofirregularities, for example, an unpaved road. Because of the high numberof irregularities, the instances in which energy may be recovered fromthe suspension system may be high and the user may select the secondmode. In a fourth example, the user may select a “fuel economy” mode,which instructs the processor to put a preference on utilizing thesecond mode. In this example, the user does not instruct a particularmode to operate in, but instructs the processor to prioritize one modeover another and allows the processor to determine the appropriate modebased on the driving scenario. In a fifth example, the processor mayselect to operate in the fourth mode for increased flexibility whereflow is directed to both the damper valve 166 and the regeneration valve170. In this example, the processor may function to determine thepercentage of fluid that is directed to the damper valve 166 and to theregeneration valve 170. For example, the amount of damping force that isprovided by the pump 190 may be an amount that is determined by thecharacteristic of the pump 190 (such as the initial starting pressurenecessary). If an increased damping force is necessary, the processormay determine to route more fluid to the damper valve 166. Similarly,the because the damper valve 166 and the pump 160 may be thought of asproviding damping force in parallel to the suspension system, theprocessor may determine a desired amount of damping force and evaluate apercentage flow combination between the damper valve 166 and pump 160 toachieve the desired damping force. In a sixth example, the processor maydetect that the pump 190 is malfunctioning and may determine to directall fluid flow into the damper valve 166. However, any other suitableselection of the operation modes of the regenerative suspension strutsystem 101 may be used.

As described above, the pressure in the compressible fluid 102 used todrive the pump 190. However, energy is used to direct fluid 102 backinto the first volume 134 to replenish the volume in the first volume134 during the rebound stroke. To improve the fuel economy of thevehicle, the pressure at which fluid 102 is directed back into the firstvolume 134 is preferably substantially less than the pressure of thefluid 102 used to drive the pump 190, which results in a net positiveenergy recovery in the regenerative suspension strut system 101. Therate and/or pressure at which the fluid 102 is directed back into thefirst volume 134 during the rebound stroke is preferably activelycontrolled to increase energy efficiency. Similarly, the rate and/orpressure at which the fluid 102 is displaced from the second volume 126is preferably also actively controlled to balance with the pressure offluid injected into the first volume 124. In typical suspension strutsystems, the rebound stroke is passive and is substantially dependent onthe type of road irregularity, for example, the shape of the bump on theroad. In other words, energy that could have been captured from thecompression of the suspension due to the bump in the road is used in theuncontrolled retraction of the suspension after the bump. Bysubstantially controlling the rebound stroke through controlling therate and/or pressure at which fluid 102 is injected into the firstvolume 134 and/or through controlling the rate and/or pressure at whichfluid 102 is displaced from the second volume 136, energy recovery inthe regenerative suspension strut system 101 may be substantiallyimproved over a typical suspension system. This control may be obtainedby controlling the fluid flow rate with the pump 190, wherein the pump190 controls fluid flow into the first volume 134 indirectly bycontrolling the fluid ingress into the reservoir cavity. Alternately,the pump 190 may be directly coupled to the first volume 134, whereinthe valve plate further includes a fourth flow path coupling the pumpoutlet to the first volume 134 and a second replenishment valve,disposed within the fourth flow path, that allows one-way fluid flowfrom the pump to the first volume 134.

The pump 190 and damper valve 166 may also function to provide aretractive force on the regenerative suspension strut 101 100. Typicalsuspension struts are configured to provide a force to suspend thevehicle, or, in other words, a force to extend the strut, and compressesonly when there is an external force such as a bump or a turn, andtypically do not provide a force to compress the strut, or a retractiveforce. An active suspension utilizing a single acting cylinder actuatormay change the height of the strut, but cannot provide a retractiveforce unless the strut is fully extended. By facilitating control overthe compressible fluid flow to/from the second volume 136, theregenerative suspension strut system 101 is able to provide such aretractive force. As shown in FIGS. 9 and 10, fluid flow from the firstvolume 134 to the second volume 136 results in an increased pressurewithin the second volume 136, which is relieved when the fluid 102 isforced through the damper valve 166 and/or pump 190 and damped. However,if an imbalance between the flow rate out through the damper valve 166and/or the pump 190 and flow rate into the second volume 136 is present,the pressure within the volume of fluid contained within the secondvolume 136 cannot be relieved, and a force to push the cavity piston 122back towards the valve plate 160 is present, providing a retractiveforce. Varying the amount of fluid that is bled through the damper valve166 and/or directed to pump 190 may control this retractive force. Thismay be particularly useful if a particular position of the strut that isshorter than the fully extended is desired. An additional retractiveforce may be achieved by driving the pump 190 to pump fluid into thesecond volume 136, as shown by the dashed line 4 a in FIG. 14.Alternatively, if the pump 190 is driven to pump fluid 102 out of thesecond volume 136, the retractive force may be decreased tosubstantially zero and/or a force to extend the suspension strut 100 mayresult. This pull force may be used to relatively quickly restore theheight of the triple tube strut 100 or for any other suitable use.However, any other suitable method to produce a retractive force in thesuspension strut 100 may be used.

As shown in FIG. 14, the regenerative suspension strut system 101 of thepreferred embodiments functions to recover a substantial amount ofenergy used to operate the triple tube strut 100. The X-axis of FIG. 14represents displacement frequency seen in the suspension strut 100, forexample, from irregularities in the road while the Y-axis represents theforce that the suspension strut provides on the vehicle, in other words,the suspending force. Curve 1 represents the equilibrium position of thetriple tube strut 100, which changes depending the weight of thevehicle, the payload of the vehicle, or any other suitable parameter.Curve 2 represents the force preferably provided by the regenerativesuspension strut system 101 to the vehicle (for example, through asuspension strut 100 of the triple tube strut construction), in otherwords, the operating region of the suspension strut 100, and Curve 4represents the retractive force provided by the suspension strut 100, asdescribed above. The shaded region 3 describes the operating region ofthe suspension strut from which energy may be recovered, in particular,the energy from irregularities on the road. Portion 3A represents theregion of irregularities that require suspension response speeds thatmay be provided by the pump 190 while Portion 3B (cross-hatched)represents the region of irregularities that require a faster response,for example, when the damper valve 166 is used to provide the dampingforce. In typical driving scenarios, a majority of the irregularitiesencountered may require suspension response speeds that may be providedby the pump 190. As a result, a substantial portion of the energy fromroad irregularities may be recovered. The substantially direct linkagebetween the suspension strut 100 and the pump 190 also decreases theamount of parasitic energy losses within the regenerative suspensionstrut system 101, which increases the efficiency at which energy may berecovered.

As shown in FIG. 15, the regenerative suspension strut system 101 of thepreferred embodiments may also include a second compliant volume 192that is preferably isolated from the system when fluid 102 is activelydirected to the pump 190 and may be connected when fluid 102 is notdirected to the pump 190. The second compliant volume 192 receives fluid102 from damper valve 166 to alleviate the pressure of the fluid 102that would otherwise be used to drive the pump 190. In particular, thesuspension strut 100 may be operated at higher pressures when fluid isactively directed to the pump 190 because increased pressure in thefluid 102 is substantially quickly alleviated through the pump 190.However, when fluid is not actively directed to the pump 190, thepressure within the triple tube strut 100 may be too high for passiveoperation (e.g., the strut 100 may be too stiff) and fluid may then bedirected to the second compliant volume 192 to decrease the pressurewithin the suspension strut 100. This embodiment preferably utilizes thethird variation of the damper valve 166 (such as that shown in FIG. 7B),but may alternately utilize any variation of the damper valve 166 asdescribed above. However, any other suitable arrangement of the fluidflow to allow both internal damping through the damper valve 166 andexternal damping through the pump 190 may be used.

As described above, the pump 190 may function to direct fluid back intothe suspension strut 100 to replenish flow within the suspension strut100. Alternatively, the regenerative suspension strut system 101 mayinclude a reservoir 194, as shown in FIG. 16, from which the suspensionstrut 100 may draw fluid 102 to replenish the fluid 102 within thesuspension strut 100. In this variation, the suspension strut 100 mayfunction substantially similarly to a pump that pumps fluid 102 atsubstantially high pressures during the compression stroke into the pump190 to drive the pump 190 and recover energy, and to draw fluid from thereservoir 194 at a substantially lower pressure during the reboundstroke. During the compression stroke, the pump 190 functions to dampenfluid flow to provide a damping force and during the rebound stroke, thereservoir 190 provides fluid at a lower pressure than the fluid used todrive the pump 190 to recover energy, satisfying the pressurerelationships for energy recovery as described above. In this variation,the regeneration valve 170 preferably directs fluid 102 during thecompression stroke from the suspension strut 100 into the pump 190 andpreferably directs fluid 102 from the reservoir 194 into the suspensionstrut 100 from the reservoir 194. This variation of the regenerativesuspension strut system 101 is preferably otherwise substantiallysimilar to the variations as described above.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

We claim:
 1. A strut system comprising: a compressible fluid; a strutcomprising: an inner tube defining an inner cavity, the inner cavitycontaining a portion of the fluid; a secondary tube disposed coaxiallyaround the inner tube; a housing tube disposed coaxially around thesecondary tube; an intermediary cavity defined between the inner tubeand the secondary tube, the intermediary cavity containing a secondportion of the fluid, wherein the intermediary cavity is fluidly coupledto the inner cavity; a reservoir cavity defined between the secondarytube and the housing tube, the reservoir cavity containing a thirdportion of the fluid; a piston, having an aperture through the pistonthickness, that is disposed substantially coaxially within the innertube, and separates the inner cavity into a first volume and a secondvolume, wherein the aperture allows fluid communication between thefirst volume and the second volume; a one-way aperture valve within theaperture that allows fluid flow from the first volume to the secondvolume; a displacement rod, coupled to the piston, that extends throughthe second volume; a valve plate coupled to the strut, the valve plateincluding: a damping flow path fluidly coupling the intermediary cavityto the reservoir cavity; a replenishment flow path fluidly coupling thereservoir cavity to the inner cavity; a damper valve within the dampingflow path that damps fluid flowing therethrough; and a one-wayreplenishment valve within the replenishment flow path that allows fluidflow from the reservoir cavity to the inner cavity.